<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .outer {
            width: 200px;
            height: 200px;
            border: 1px red solid;
        }

        .inner {
            box-sizing: border-box;
            background-color: red;
            width: 100px;
            height: 100px;
            border: 1px red solid;
            /*margin-top: 20px;*/
            /*margin-left: 20px;*/
            /*margin: 10px 20px 30px;*/

            /*margin-right: 40px;*/

            padding-top: 20px;
            /*padding-left: 20px;*/
        }
    </style>
</head>
<body>
<!--div.outer按tab-->
<div class="outer">
    <div class="inner">
        巧克力
    </div>
</div>
</body>
</html>